This invention relates to a process and the mechanisms for controlling the temperature and heat balance of molds through the use of heating and/or cooling devices.
In the foundry literature as well as in practice many methods are known which attempt to influence the heat balance and temperature of molds, in order to produce pore-free, fine-grained, stress-free, crack-free castings as well as to decrease the cycle time of casting. All of these methods are slow and ineffective or totally unable to control the mold temperature and heat flow within sufficiently small regions of the mold or to control the sequence of cooling from point to point within the mold during one casting cycle. Such control is essential to promote controlled, directional solidification of the individual casting.
As described by Seidel, "Zweckmassiges Heizen und Kuhlen von Druckgiessformen mit entsprechenden Temperatur-Regelgeraten" GIESSEREI, 25, 1973 pp. 794-797 heating and cooling devices with temperature control have been employed in die casting molds to increase the production rate sufficiently to offset the large investment in molds and auxiliary heating and cooling equipment.
The installation of heating and cooling devices in the die casting molds in this instance are expensive due to extensive machining and sealing requirements. Variations in temperature within the die casting mold are in this case ineffective in providing directional solidification of the individual casting, indeed controlled solidification is not possible and not considered due to the extremely short time required for solidification.
An article published by Meyer, e.a., "Calcul des Canaux de Refroidissement" FONDERIE, July, 1976 pp. 251-264 describes the possibilities of mathematically establishing the dimensions of cooling channels for die casting molds. In this instance the aim was to establish a constant mold temperature after a given number of casting cycles to achieve an increase in the rate of production.
Thus, there still exists a need for a process and the mechanisms for promoting controlled, directional solidification of the single casting to insure pore-free, high-quality products at low cost. The process and mechanisms described in this invention fulfill the conditions necessary for developing controlled, directional and accelerated solidification.